Abstract
Entanglement is one of the most studied properties of quantum mechanics for its application in quantum information protocols. Nevertheless, detecting the presence of entanglement in large multipartite sates continues to be a great challenge both from the theoretical and the experimental point of view. Most of the known methods either have computational costs that scale inefficiently with the number of particles or require more information on the state than what is attainable in everyday experiments. We introduce a new technique for entanglement detection that provides several important advantages in these respects. First, it scales efficiently with the number of particles, thus allowing for application to systems composed by up to few tens of particles. Second, it needs only the knowledge of a subset of all possible measurements on the state, therefore being apt for experimental implementation. Moreover, since it is based on the detection of nonlocality, our method is device independent. We report several examples of its implementation for well-known multipartite states, showing that the introduced technique has a promising range of applications.
Highlights
Entanglement is the key ingredient for several protocols in quantum information theory, such as quantum teleportation [1], quantum key distribution [2], measurementbased quantum computation [3], and quantum metrology schemes [4]
Determining the state of large quantum systems is impractical in experiments, given that quantum tomography implies measuring a number of observables that increases exponentially with the number of systems, e.g., 3N observables even in the simplest case of N qubits [6]
It can be applied to any set of observed correlations and can be implemented by semidefinite programing involving a number of variables that grows polynomially with N
Summary
Entanglement is the key ingredient for several protocols in quantum information theory, such as quantum teleportation [1], quantum key distribution [2], measurementbased quantum computation [3], and quantum metrology schemes [4]. There are techniques capable of deriving a witness for any generic entangled state, which can be constrained to the available set of data [12], or adapted to require the minimal amount of measurements on the system [13] They always involve an optimization procedure that runs on an exponentially increasing number of parameters. It can be applied to any set of observed correlations and can be implemented by semidefinite programing involving a number of variables that grows polynomially with N All these nice properties become possible only because our method for entanglement detection is a relaxation of the initial hard problem.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
